[time-nuts] PICDIV build

[Tom Van Baak]

Anders,

Nice work.

Your output level is low because the 3.3 V output of the PIC gets cut in half by the series 50R on your board and the 50R termination. But 700 mV into 50R seems way too low. Something's not right.

FYI: see how John handles input and output in the TADD-2-mini:

https://www.tapr.org/kits_t2-mini.html
http://www.tapr.org/~n8ur/T2_Mini_Manual.pdf

That board ships with PD17 [1] and most of the dividers I design to be pin compatible with his PCB. For example, the 10 MHz to 32 kHz divider [2] that we were talking about a few weeks ago can be used with the TADD-2-mini.

You can use the same trick he did to parallel multiple outputs to gain higher output levels. The comments [3] in PD09 chip say that you can use pin3 and pin6 in addition to pin7 for output. So combine each pin through its own 50R to a common output BNC. It also helps that he runs the board at 5 V and not 3.3 V.

/tvb

[1] http://leapsecond.com/pic/src/pd17.asm
[2] http://leapsecond.com/pic/src/pd30.asm
[3] http://leapsecond.com/pic/src/pd09.asm

----- Original Message ----- 
From: "Anders Wallin" <anders.e.e.wallin at gmail.com>
To: "Discussion" <time-nuts at febo.com>
Sent: Friday, April 15, 2016 11:29 PM
Subject: [time-nuts] PICDIV build


> hi all, I wrote down some notes on a recent PICDIV build and measurements:
> http://www.anderswallin.net/2016/04/picdiv-frequency-divider/
> 
> If/when I make v2 of this board:
> - any suggestions for boosting the output amplitude of both 1PPS and 10MHz
> CMOS? Something that drives 3.3Vpp into 50R with ~few ns rise time?
> - any obvious mistakes that cause the phase-noise observed? Mostly I think
> 50/100Hz and harmonics would be nice to suppress..
> 
> thanks!
> Anders